Gaithersburg’s environmental experts are determined not to let algae blooms coat the surface of Lake Varuna this summer and have plans to use a new method to control it.
A copper sulfate spray will be used to mitigate the algae that seems to overtake the lake at the entrance to the Lakelands each summer. The suggestion came from Dan Terlizzi, water quality specialist with the University of Maryland’s Department of Agriculture, who met with city representatives lakeside on June 9.
The spray is a chemical treatment that is applied directly to the algae. Only one third of the pond is treated at one time. Killing too much of the algae at one time depletes oxygen in the water, which could kill fish within the pond. Officials will need to test the water’s alkalinity since the toxicity of copper to fish increases as the total alkalinity decreases.
“There may be bigger risks of not managing these algae mats than there are with the copper treatment,” Terlizzi said. “Prevention techniques are great but involve more time and money, which are difficult right now.”
Terlizzi is suggesting a light spray application on the algae mats to keep the amount of copper sulfate needed to a minimum.
“It is difficult to say there are no other effects, but they will be minimal and probably not even detectable,” Terlizzi said. “When settlers were heading out West in wagons, they were advised to place a copper coin and a silver coin in water barrels — copper inhibited algal growth and silver apparently for inhibiting bacteria. This idea has been around a while and can be safe and effective.”
The use of copper sulfate is one of the algae treatment methods recommended by Maryland Cooperative Extension Service.
“Any kinds of pesticide is a last resort for us,” said Wally DeBord, Gaithersburg’s Public Works operations director. “There is a tremendous amount of nutrients going to Lake Varuna. The algae needs to be controlled because it is a stormwater management pond.”
City officials have tried other methods to control algae in the pond off Lakelands Drive. In May the city floated six bales of barley straw in an effort to prohibit algae growth.
“This just gives us another tool in our toolbox,” said Gaithersburg’s Public Works Director James Arnoult.
Aeration bubblers, like those found in Lake Sheila in Kentlands are also an option for Lake Varuna. In the past, city officials said an aerator was too expensive and would be ineffective in Lake Varuna. However, Arnoult said results of a bathemetric study of the lake to determine sediment amounts and depth show an aerator could be useful.
“It is something we will consider,” Arnoult said.
Terlizzi said the aerator would help the lake’s water quality issues.
The bathemetric study showed Lake Varuna is at its deepest measuring 10 feet closest to Lakelands Drive. The center of the lake measures about 5 feet in depth, and it shallows on the lakeside toward Midtown.
Gaithersburg Environmental Specialist Gary Dyson said he is applying for grant funding to do wetlands planting on the shallow side of the lake to help control sediment flow.
It’s not just algae and sediment runoff that is working against Lake Varuna. Beavers have been plugging up the lake’s low flow outfall pipe. This reduces the capacity of the lake to handle stormwater and could be a safety issue.
Work has also now begun to install a fence around the low flow outfall pipe preventing beavers from building a dam there. The lake will be lowered for workers to get access to that area.